Previous work on this project has indicated that joint afferent neurons from cat knee have mechanical sensitivity which differs qualitatively between regions of the capsule. Afferents from the anteromedical capsule are purely pressure-sensitive, while those from the posterior capsule appear to be stretch-sensitive. In the proposed experiments, the stress or strain sensitivity of single afferents from different regions of the knee would be determined by studying the responses of joint afferents recorded in isolated strips of either medial or posterior joint capsule, surgically removed from the knee and studied in vitro. Various components of stress can be independently manipulated, and the sensitivity of afferents directly measured. Further, the receptors mediating these responses would be identified by excising small sections of capsule containing a receptor with known properties, and staining, fixing, and sectioning the excised block. In the third components of the proposal, the mechanical sensitivity of c fiber afferents in joint nerves would be tested.